Fine Gael has demanded an explanation from the Minister for Justice over his comments concerning the tax affairs of the Flynn family.
On Saturday, Mr McDowell said he had been aware for some time of allegations that Mayo TD Ms Beverley Cooper-Flynn helped her father, former minister Mr Pádraig Flynn, invest money offshore and evade tax.
Fine Gael leader Mr Enda Kenny said: "It is legitimate to ask how Minister McDowell became aware of these allegations, which are currently being examined by the Mahon Tribunal".
"When did he learn of these allegations? What has he done about the allegations since he became aware of them and specifically did Minister McDowell inform the Taoiseach of his knowledge of these allegations?" asked Mr Kenny.
He said: "It is becoming more and more obvious that the PD watchdog has effectively turned into a Government guard dog."